Dyeing polyacrylonitrile and cellulosic blends with vat and cationic dyes



3,085,848 Patented Apr. 16, 1963 ice 3,085,848 DYEING POLYAQRYLONITRILE AND CELLULOS IC BLENDS WKTH VAT AND CATIONIC DYES Everett H. Hinton, Jr., Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Filed Jan. 20, 1959, Ser. No. 757,821 9 Qlairns. (i. 8-21) This invention relates to a one-step continuous process for dyeing blends of acrylic and cellulosic textiles and more particularly to improved techniques for preparing and using stable dispersions of vat and cationic dyes for dyeing these blends.

Fabrics and yarns composed of acrylic and cellulose type fibers have many desirable properties, but heretofore the only satisfactory method available for dyeing such a blend has involved two steps comprising the separate application of two classes of dyes for the two fibers. This two-step process is costly and involves too much handling of the yarns or fabrics.

An object of this invention is to provide a continuous one-step dyeing process for acrylic/cellulosic textile blends. Another object is to provide a stable dispersion of vat and cationic dyes which may be applied in one step to these textile blends. Another object is to provide a dye liquor which will permit the dyeing of blends of acrylonitrile polymer and cellulosic textiles simultaneously in a full range of union as well as cross-dyed shades. Other objects will be apparent as the description of the invention proceeds.

The above and related objects are accomplished by providing a stable aqueous acidic dispersion comprising a vat dye, a cationic dye, a nonionic dispersing agent, an anionic dispersing agent, and an organic liquid swelling agent foracrylonitrile polymer fibers. The invention also comprises the proper sequence of steps in the preparation of the stable aqueous dispersion of the two dyes. The invention further involves the continuous process of dyeing acrylonitrile polymer/cellulosic textile blends comprising the steps of padding the above-mentioned stable aqueous dispersion on the textile preferably at room temperature, subjecting the textile to a steaming treatment, reducing the vat dye, rinsing, oxidizing the vat dye, then removing the excess treating agents and drying the textile.

A general procedure for preparing .a stable dispersion of the two dyes is as follows:

(1) The cationic dye is mixed with the nonionic dispersing agent in hot water. Sufiicient acid is added to give a pH in the final stable dispersion in the preferred range of 4.5-5.0. Then cool water is added to bring the temperature of the solution to room temperature before further mixing.

(2) In a separate container the polyacrylonitrile fiber swelling agent is mixed in hot water with a buffering agent such as sodium acetate to adjust the final pad liquor to a pH of 4.5-5.0.

(3) Solution 2 is added to solution 1.

(4) The vat dye and the anionic dispersing agent are added to a separate vessel containing water at room temperature and an antifoam agent, keeping the contents vigorously agitated during mixing by using a colloid mill, a propeller driven stirrer, or other eiiective mixing means.

(5) Mixture 3 is added to dispersion 4 with continuous vigorous stirring.

(6) Additional cool water is added and the pH is adjusted if necessary to 4.5 to 5.0.

At this stage it is desirable to spot test the aqueous dispersion by putting one drop on a piece of filter paper to be certain it is a thorough dispersion of the two dyes.

This can be checked easily with the naked eye by noticing it the dye spreads uniform color over the area of the filter paper.

An adequate procedure is described below for the steps necessary for applying the above dispersion to textile blends by a continuous one-stage dyeing process.

(1) The fabric is padded with the above prepared dye liquor by passing the fabric into the aqueous dispersion of dye liquor maintained at room temperature and contained in a padding vessel.

(2) The wet fabric is then passed into a steam chamber for an exposure time of about one minute to allow the cationic dye to go on the polyacrylonitrile fibers.

3) The fabric is then passed into a reduction bath to accomplish dyeing of the cellulosic fibers. A conventional reduction bath contains an aqueous medium, sodium hydroxide, and sodium hydrosulfite as a reducing agent for the vat dye.

(4) The fabric then is rinsing baths.

5) The fabric is then passed through an oxidizing bath to insolubilize the vat dye. A conventional oxidizing bath contains an aqueous solution of sodium dichromate and acetic acid.

( 6) The fabric is rinsed in an aqueous bath.

(7) The fabric is scoured in an aqueous medium to remove excess dye and to agglomerate the vat dye molecules inside the fabric.

(8) The fabric is rinsed in an aqueous bath to remove scouring agents.

(9) The fabric is then dried.

Typical cationic (i.e. basic) dyes which may be used to dye the acrylic component fibers in the present invention include the following:

passed through two aqueous Sevron Blue B Sevron Blue 20 Du Pont Victoria Green Crystals. Du Iont Crystal Violet Basic Blue 21-- Basic Blue 22- Basic Green 4--.- Basic Violet 3..-...... 42, 555

Typical vat dyes which may be used in the present invention for dyeing the cellulosic component fibers include the following:

New Vat Dye Old 0.I. No. 0.1. No.

Sulfanthrene Pink FFD Paste Vat Red 1 73, 360 "Sulfanthrene Pink FF Vat Red 1.. 73, 860 PonsoY' Blue BOS Double Paste Vat Blue 6... 69, 825 Ponsol Yellow 5GLL Paste... Vat Yellow 22 Ponsol Orange RRI Paste... Vat Orange 2 59, 705 Ponsol Brown RBT Paste...- Vat Brown 1. ,800 Ponsol Black 3G Double Past Vat Black 13- Ponsol Gray R Paste Vat Black 14.- "Ponsol Navy Blue Double Paste.--.- Prototype 522 71, 200

The vat dyes are normally water-dispersible pigments and may be selected from the classes of anthraquinone and indigoid dyes, among others. The cationic dyes are normally soluble in water and usually contain a quaternary nitrogen atom. They may be selected from the classes of triphenylmethane, cyanine, methine and xanthrene dyes, among others. The old and new CJI. numbers given above in the lists of dyes refer to the dyes listed in Colour Index, Second Edition, 1956, in four volumes, compiled jointly by The Society of Dyers and Colourists and The American Association of Textile Chemists and Colorists.

The role of the anionic dispersing agent is critical in keeping the dyes dispersed in the aqueous medium. The anionic dispersant may be used in liquid, powder or paste form and should be chosen to have a minimum effect in retarding the cationic dye under the pad-steam dyeing conditions. Otherwise the anionic negatively charged radical is liable to have more affinity for the positively charged dye than the negatively charged fiber has for said dye. Typical of the suitable anionic dispersants useful in this invention are sodium oleate, potassium oleate, sodium palmitate, potassium palmitate, the sodium salt of naphthalene sulfonic acid condensed with formaldehyde, cetyl betaine and the like.

The nonionic dispersing agent used in the stable dispersion is critical in maintaining the stability of the dispersion during the dyeing of the fabric. It is particularly important to have it present in the dispersion when oppositely charged radicals are present (i.e., the negatively charged anionic dispersant, the positively charged cationic dye, and the negatively charged dispersant normally present in commercially available vat dyes). Typical neutral nonionic dispersants include water-soluble polyoxyethylenes, such as those formed by reacting 18 moles of ethylene oxide with 1 mole of a mixture of long-chain fatty alcohols containing principally C14, C and C alcohols, 25% of which are unsaturated alcohols, or those obtained by reacting 20 moles of ethylene oxide with one mole of a mixture of 75% oleyl alcohol and 25 stearyl alcohol, or those obtained by reacting 25 moles of ethylene oxide with one mole of a mixture of about 50% C saturated fatty alcohol, about 25% C unsaturated fatty alcohol and about 25% C unsaturated fatty alcohol, or the like.

The liquid swelling agent for acrylonitrile polymer fibers is required in the pad-steaming step to apply the cationic dye to this fiber rapidly and continuously. These swelling agents or dye carriers are well known for acrylonitrile polymer and copolymer fibers and include ethylene carbonate, propylene carbonate, gamma-butylrolactone, trimethylene carbonate, and the like.

In order to obtain maximum exhaustion of and protection for the cationic dye, the stable aqueous dispersion of the vat and cationic dyes should be adjusted to a pH range of 4.5-5.0. This is accomplished by adding to the dispersion a suitable acid such as phosphoric, acetic, formic, or citric acids. A non-volatile acid is preferred, phosphoric acid being particularly suitable because of its low cost and low volatility.

The improved dyeing procedure of this invention may also be carried out by substituting for the vat dye in the dispersion above any anionic dye such as an acid dye, a direct dye, or a disperse or neutral dye which contains an anionic dispersant, when it is desired to dye blends of acrylic fibers with other fibers known to be dyeable with the indicated substitutions.

The improved dyeing technique of this invention may be employed to union dye or cross-dye blends of any acrylic and cellulosic textiles. Typical of the fabrics and textile materials which may be dyed include woven, knit, and non-woven fabrics, batts, felts, tow, yarn, warp sheets, and the like.

The acrylic textile is preferably in the form of fibers or filaments of acrylonitrile polymer or filamentary materials composed of at least 80% by weight acrylonitrile polymer with up to 20% of copolymerized ingredient such as methyl acrylate, vinyl acetate, vinyl chloride, sodium styrene sulfonate, vinyl pyrrolidone, vinyl pyridine, and the like. However, the dyeing technology of this invention also may be applied when using any negatively charged fiber normally dyeable with cationic dyes in place of the acrylonitrile polymer fiber. The other ingredient in the textile material may be any cellulosic fiber or filament such as cotton, viscose rayon, cellulose acetate, cellulose ethers, or other cellulosic material which is dyeable with vat dyes or their substitutes.

The following examples are given to illustrate specific embodiments of this invention without limiting the scope thereof. All ingredients are expressed by weight unless otherwise specified.

Example I 160 yards of a woven broadcloth fabric weighing 30 lbs. made from spun yarns of a blend of of staple acrylonitrile copolymer fibers (94% acrylonitrile, 5.7% methyl acrylate and 0.3% sodium styrene sulfonate) and 20% cotton was cross dyed yellow-brown with 25 gals. of dye liquor. The cotton dyed brown and the acrylic fibers yellow. Each gallon of dye liquor was made by dissolving 2.67 oz. of Sevron Yellow L, 0.9 oz. of the condensation product of about 20 moles of ethylene oxide with one mole of a mixture of long-chain fatty alcohols containing principally C and C alcohols, approximately 50% of said mixture being unsaturated alcohols, and 0.48 oz, of phosphoric acid in .3 gal. of hot water, followed by the addition of .2 gal. of cool water.

In a separate vessel 16.7 oz. of ethylene carbonate and 0.67 oz. of sodium acetate were dissolved in .1 gal. of hot water. The latter solution was added to the solution of cationic dye and the total volume brought to 0.7 gallon by addition of .1 gal. of water.

A third mixture was prepared by dispersing 5.34 oz. of Ponsol Brown RBT Paste and 0.53 oz. of sodium oleate green soap (dispersed in .1 gallon of cool water) in another 0.1 gallon of water containing a small amount of an antifoam agent, while vigorously stirring the mixture. This dispersion was made up to a volume of 0.3 gallon by addition of cool water.

The dispersion of cationic dye was added to the dispersion of vat dye with continuous vigorous stirring using a propeller stirrer. After combination of these two dispersions, the pH was checked and adjusted to a pH of 5.0 by addition of more phosphoric acid. The final mixture was also checked for complete dispersion by spot testing on a piece of absorbent filter paper.

The broadcloth fabric was padded in a vessel containing the stable dispersion of the two dyes maintained at room temperature. There was a wet pickup of 18 lbs. or 60% on the fabric weight. The wet fabric was passed into a steam chamber at 220-222 F. for an exposure time of 55 seconds. Then the fabric was passed directly into a Williams Unit reduction box having a capacity of gallons. The box contained 8 quarts of 50% aqueous sodium hydroxide and 8 pounds of sodium hydrosulfite. The temperature of this reduction box was maintained at F. An additional 0.27 oz./gal. of the vat dye was added to the reduction box.

The fabric was then passed directly through two aqueous rinsing baths. After rinsing, the fabric was passed through an oxidizing bath containing an aqueous solution of sodium dichromate and acetic acid.

The fabric was then rinsed in an aqueous bath and continuously scoured at the boil in an aqueous bath containing 0.25 oz./gal. of green soap, 0.25 oz./gal. of soda ash, and 0.13 oz./ gal. of sodium lauryl sulfate wetting agent. After a final rinse in an aqueous bath, the fabric was dried on a pin tenter with overfeed at 270 F. to a width of 38". The dyed fabric exhibited a satisfactory yellowbrown cross-dyeing with no serious shading on the cotton.

Example 11 A sample of the same woven broadcloth fabric of acrylonitrile fibers and cotton fibers was union dyed yellow using the same dyeing procedure and proportions of fabric and dye liquor as described in Example I. The stable dispersion of the cationic and vat dyes was prepared by the same procedure with only the following changes in the ingredients used for preparing the dispersion. The cationic dye solution was prepared using 2.67 oz. of Sevron Yellow L and 0.43 oz. of the same non-ionic dispersing agent as used in Example I. The vat dye dispersion was prepared using 0.67 oz. of Ponsol Yellow SGLL Paste and 0.48 oz. of sodium oleate green soap. The resulting union-dyed fabric was a clear shade of yellow and showed no dyeing non-uniformities.

Example III A six gram sample of 70 sq. in. of the same type of woven broadcloth fabric as that used in Example I was cross dyed, except that the spun yarns were prepared from 80% of the same staple acrylic copolymer as that of Example I and 20% of regenerated cellulose staple. The same dyeing procedure and 500 grams of the same dye bath was employed. The resulting cross-dyed fabric exhibited a satisfactory shade of yellow on the acrylic fibers and brown on the cellulosic fibers.

The chief advantage of this invention is that it provides a continuous one-step dyeing process for dyeing both acrylic and cellulosic fibers simultaneously in a full range of union as well as cross-dyed shades. Another advantage is that it provides a stable dispersion of two classes of dyes, said dispersion being stable up to several hours for dyeing large yardages of textiles. The novel stable dye dispersion of this invention is a highly uniform dispersion free of color agglomerates which yields good clear, bright shades in blends of acrylic and cellulosic textiles. The use of mixtures of two classes of dyes which are not substantially stable causes some agglomeration of color particles in the dispersion which produces speckled fabrics and nonuniform dyeings.

It will be apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

I claim:

1. A dye bath suitable for dyeing textiles composed of acrylonitrile polymer and cellulosic fibers, which com- 5 prises a stable aqueous dispersion of a vat dye, a cationic dye, a non-ionic dispersing agent, an anionic dispersing agent and an organic liquid swelling agent for the acrylonitrile polymer fibers, the said dye bath having a pH between about 4.5 and 5.0.

2. The dye bath of claim 1 in which a non-ionic dispersing agent is a polyoxyethylene.

3. The dye bath of claim 1 in which the anionic dispersing agent is a soap.

4. The dye bath of claim 1 in which the liquid swelling agent is a lower alkylene carbonate.

5. The process of dyeing textiles made from acrylonitrile polymer and cellulosic fibers which comprises passing textile material through the dye bath of claim 1, passing the wet material into a steam chamber, passing the material through a bath containing a reducing agent, washing, passing the material through a bath containing an oxidizing agent, and thereafter washing, scouring and drying the said material.

6. The process of claim 5 in which the textile material is exposed to steam in the steam chamber for about a minute.

7. The process of claim 5 in which the non-ionic dispersing agent is a polyoxyethylene.

8. The process of claim 5 in which the anionic dispersing agent is a soap.

9. The process of claim 5 in which the liquid swelling agent is a lower alkylene carbonate.

References Cited in the file of this patent Clarke: American Dyestuif Reporter, Aug. 29, 1955, pp.63l- 640.

Neary: American Dyestutf Reporter, Aug. 26, 1957, pp. 625-632.

A.A.T.C.C. Monograph No. 2, Application of Vat Dyes, American Association of Textile Chemists and Coloris-ts 1953). 

1. A DYE BATH SUITABLE FOR DYEING TEXYILES COMPOSED OF ACRYLONITRILE POLYMER AND CELLULOSIC FIBERS, WHICH COMPRISES A STABLE AQUEOUS DISPERSION OF A VAT DYE, A CATIONIC DYE, A NON-IONIC DISPERSING AGEN, AN ANIONIC DISPERSING AGENT AND AN ORANIC LIQUID SWELLING AGENT FOR THE ACRYLONITRILE POLYMER FIBERS, THE SAID DYE BATH HAVING A PH BETWEEN ABOUT 4.5 AND 5.0. 